Wind power

Question 1

What is Capacity Coefficient (CC) and why is correct choice of rated wind speed important?

Answer 1

• defined as the rate of average to rated power
  Choosing rated wind important as if it is increased:
• energy capture increases
• capacity coefficient decreases
• capital cost increases

Question 2

What is the Betz limit and why isnt it ever actually reached?

Answer 2

• 59.3%
• Cant be reached due to losses in the drivetrain and generator as well as energy contained in blade tip vortices and general swirling in the wake

Question 3

What is the tip-speed-ratio

Answer 3

• Employed when designing turbines so the max amount of energy can be extracted from the wind using a particular generator, three bladed designs achieve max power efficiency
• more blades, the slower the turbine will turn

Question 4

How can wind turbines be optimised?

Answer 4

Digital modelling - computer models to find wake effects and then optimal distances between turbines
Contra-rotation - turbines arranged to rotate in different directions